FIG. 1 is a front elevation view illustrating a conventional elevator car, and FIG. 2 is a side view showing the car door apparatus in FIG. 1, with car body 1 being shown in cross-section. As illustrated, elevator car entrance 2 is provided at the front face of car body 1. Door frame 3 extends along the width of entrance 2, and is fixed to car body 1 above entrance 2. Door motor 4 having motor pulley 5 is mounted on door frame 3. Reduction pulley 6 having a larger diameter than motor pulley 5 has belt 7 wound between motor pulley 5 and reduction pulley 6. Drive pulley 8 has a smaller diameter than and is coaxial with reduction pulley 6, can be rotated integrally with the reduction pulley 6. Following pulley 9 is provided at the door frame 3, with second belt 10 wound between drive pulley 8 and following pulley 9.
Door rail 11 extends along the width direction of entrance 2 and is attached to door frame 3. Two car doors 12 are suspended from door rail 11 through door hangers 13. Each door hanger 13 has two rollers 14 which are rotated along door rail 11. Car doors 12 are connected to second belt 10 through door hanger 13 and belt holders 15 and 16. A plurality of door shoes 17 are attached adjacent the lower edge of each of doors 12. Door shoes 17 are inserted into a groove (not shown) of sill 18 disposed at the lower portion of entrance 2. Further, car body 1 is provided with upper panel 19 and ceiling panel 20.
During operation, motor pulley 5 is rotated by door motor 4, and the rotation is transmitted to reduction pulley 6 through reduction belt 7. Drive pulley 8 is rotated with reduction pulley 6, and thus second belt 10 is circulated and following pulley 9 is rotated.
Since door hangers 13 are connected to belt 10, door hangers 13 and doors 12 are reciprocated along door rail 11 by the circulation of second belt 10 to open or close entrance 2. Doors 12 are suspended from door rail 11 and the bottom portions of doors 12 are guided by the sill groove of sill 18 during the opening and the closing of doors 12.
FIGS. 1 and 2 show a prior art device for driving a door of an elevator car, wherein door motor 4 is located above car body 1 and ceiling plate 20 of car body 1 is placed just below door motor 4. When designing the elevator car with higher ceiling plate 20, which is equipped with such a door driving device, ceiling plate 20 cannot help but interfere with door motor 4. Accordingly, the door driving device must be redesigned in order to avoid such interference. Further, large noise may occur in such a door driving device due to reduction pulley 6 and reduction belt 7 during the movement of doors 12.
FIGS. 3 and 4 show another prior art device for driving doors 2 of elevator car 1, wherein door motor 22 is disposed under horizontal portion 21b of a door frame 21 inside plane A extending parallel to vertical end face 18b of a sill, thereby eliminating interference between door motor 22 and ceiling plate 20. In this embodiment, bolts 23 hold door motor 22 in place on horizontal portion 21b of door frame 21, while vertical portion 21a extends down to attach to rail 11. Driving pulley 24 is attached to drive motor 22, and connected to following pulley 25 via belt 26. Rail 11 extends along the width of car 1, with door hangers 13 and corresponding rollers 14 being supported thereon. Doors 12 are connected to belt 26 through door hangers 13 and belt holders 15 and 16. Door shoes 17 are attached adjacent lower edge of doors 12, and are inserted into groove 18a of sill 18. The door operates as described before, with the exception being that drive motor is connected directly to driving pulley 24 without a reduction mechanism.
However, since a driving shaft of door motor 22 is not directly supported by door frame 21, vibrations caused by the rotation of the driving shaft can be applied to door frame 21 during operation of door motor 22. Further, since the distal end of the driving shaft, to which driving pulley 24 is coupled, serves as a free end, the load applied to driving pulley 24 through belt 26 during movement of doors 12 cannot be smoothly supported, thereby causing vibrations and noise.
Accordingly, a driving motor, which is configured to cause less vibration and noise, is necessary for driving a door of an elevator. Further, a device for driving a door of an elevator that does not interfere with a ceiling plate of an elevator and is compactly configured is needed.
In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that afflict elevator systems.